Conventional liquid filled plastic bottles which utilize a threaded plastic cap have typically had problems with leaking due to the cap wobbling and "backing-off" (i.e., loosening) during shipment and handling. This problem is particularly troublesome for dispensing closures such as trigger sprayers that have high profile heads which can apply leverage to back off the cap if bumped.
In an effort to alleviate the problem, excessive torque can be applied. However, this could result in the plastic threads being over stressed, thereby damaging the threads and compromising the quality of the seal. Furthermore, over torquing the closure is not possible where the closure must be rotated to a particular position or orientation.
Conventional bottle filling production lines typically torque closures to a specific load or position. This requires complicated clutch systems that sustain wear and need constant adjustment, which has a negative effect on process reliability.
Therefore, what is needed is a closure assembly having interference threads which provide a leak free seal regardless of rocking or wobbling of the closure assembly. Furthermore, what is needed is a seal created by rotating the closure to particular position rather than to a specific torque, thereby eliminating wear items and the need for adjustment resulting in improved process reliability.